Thursday, April 10, 2008

An Oil Drum Nuclear Debate Comment

kipinBluff asks.

Charles . . . Would you or your family in any way profit from the licensing of (some of) these patents to commercial accelerator design and manufacturing companies?

Answer: No.

All rights to pattens were assigned to the United States Government, Neither my father, I or any other member of the family would directly benefit from the patents my father received. Also my father never did research on the design or development of accelerators. I have no direct investments in businesses that would profit from the development of LFTR technology. I am retired. My only source of income is retirement savings and social security.

BTW, the 'proof of concept' thorium reactors at ORNL were of the order of 8-10 MWt. No 'proof of scalability'.

Quite the contrary, the factors that effect the stability of the MSR/LFTR do not change with scale and the MSRE was a very stable reactor. There are actually several types of stability that can be attributed to the MSR. The first is the chemical stability of its liquid salts fuel/carrier/coolant. http://en.wikipedia.org/wiki/Molten_salt_reactorMy father extensively researched the chemical stability of liquid fluoride salts. The chemistry of liquid fluoride salts does not change with reactor size. Gat and Dodds state:

The molten salts considered for MSRs are chemically stable. hey do not react rapidly with moisture or air. Their chemical inertness precludes accidents that are due to chemical interaction. There is no fire hazard or explosion hazard. They are also compatible and are non-corrosive with respect to suitable structural materials. The experience with the MSRE has shown that high-nickel alloys, combined with adequate oxidation potential balancing of the salt, can result in low corrosion of the structural materials.

The molten salts considered for the MSR are stable to high temperatures at low pressures. This feature allows for high efficiency with no extreme safety demands from the structure materials. Being a liquid system at low-pressure eliminates the storage of potential energy or other risk of an energetic burst or explosion. Molten salts are often used in industry as heat transfer media for their inertness and safety. There is ample experience in handling molten salts.

Small spills are not a source of a major accident as there are no violent reactions that can accompany a spill. As a spill occurs, the salt is spread out and cools more efficiently than in the insulated pipes. The salt freezes in place without spreading and is available for recovery operation. The freezing process is inherent and passive. Should there be some residual heat sources in the salt, it will stay molten until it reaches a configuration in which the thermodynamic equilibrium brings it to a freeze.

The second form of stability has to do with the stability of the nuclear process within the reactor core. In a stable reactor, it is not possible to loose control of a chain reaction:

Gat and Dodds state:

In MSRs with processing, the criticality accident is essentially eliminated (See concerns section for exceptions.). There are two factors that make an excess reactivity incident unlikely, temperature control and optimized geometry. The MSR can be temperature-controlled. The large negative temperature coefficient allows for control without control rods or other mechanically operated control mechanism. The operability of the reactor under temperature control has been demonstrated on FFR(HRT). The control rods can be used for temperature regulation. Continuous fuel processing, with the ability to externally add fissile material when needed, reduces the need for excess reactivity inventory. There is no need to compensate for burnup as the poisoning fission products are kept at (low) equilibrium. The simple design, particularly when utilizing external cooling, eliminates the possibility of shifting or rearranging materials to result in an increased reactivity. The absence of coolant per se does not provide room that could be filled with shifting fuel to increase reactivity. The MSR can be designed so that bred fuel, at a breeding ratio of 1.0, keeps the reactor at equilibrium with fertile-material feed and with no need to add fissile material. Since the fuel is also the coolant, the reactor is largely temperature-controlled regardless of the power.

The adequately-designed MSR has an optimum geometrical design for criticality in the core. The externally-cooled reactor has neither coolant nor structural materials in the core that may require design compromises and thus can truly be optimized for safety. This core optimization also assures that no criticality, or re-criticality, outside the core can occur.

None of these factors change with size.

Heat stability after an emergency shutdown is another reactor issue. Gat and Dodds note:

The MSR can be designed, with sufficiently rapid processing, that it can contain adiabatically the entire inventory after-heat without reaching boiling. Furthermore, since the fuel is the coolant, in external cooling, a LOCA has no meaning. As a rule, natural convection cooling could be designed but may not be desirable as the temperature-controlled reactor will maintain its design temperature regardless of the power. The reaction needed is to drain the fuel, by gravity, into dump tanks that are assured to retain subcriticality and have sufficient natural cooling to assure cooling of the fuel. The activation of the draining can be done by means of freeze valves that assure PINT safety for after heat removal.

Among the safety advantages for LFTR/MSRs Gat and Dodds noted:

* Simple reactor structure

* Continuous removal of fission products

* A high negative reactivity temperature coefficient that slows down chain reaction as reactor temperature rises

* The LFTR can be self-controlling

* No externally operated controls are required

* Safety can be passive

* Safety is inherent and safety features cannot be altered by tampering, and are thus fool proof

* Ultimate shut-down is accomplished by draining the liquid fuel from the reactor core

* A drain plug can be operated automatically by using a material that melts when the reactor reaches an undesirable heat level

* Core dranaged powered by gravity

* The drain container can be in a shape that prevents drained fuel from become critical

The Fluoride salt coolant is safe because:

* It does not react with water or air

* There is no fire or explosion hazards

* It is non-corrosive with respect to very desirable and suitable structural materials like carbon based materials

* They are stable to high temperatures and exert low pressure

* Liquid salts are often used in industry as heat transfer media for their inertness and safety

* In the event of an accidental spill, liquid salt freezes in place without spreading

* A core meltdown is not a problem, because the fuel is already a liquid

* Since the coolant is also the fuel, a loss of coolant accident is does not lead to fuel overheating

Again they see no issue which would be effected my reactor scale.

SkipinBluf, I am not advocating the LFTR because I would personally benefit from it. Rather, having some familiarity with the technology I see evidence that many problems with the current generation of commercial reactors would be solved by technology.

In Deep-Burn Molten-Salt Reactors, Ralph Moir of Lawrence Livermore National Laboratory, who co-authored Edward Teller's last paper, together with T. J. Dolan, of Idaho National Engineering and Environmental Laboratory, Sean M. McDeavitt of Argonne National Laboratory, D. F. Williams and C. W. Forsberg of Oak Ridge National Laboratory, and E. Greenspan and J. Ahn of the University of California, Berkeley wrote,

"Molten salt reactors have the potential of meeting the goals of Generation IV reactors better than solid fuel reactors. They also have the potential of meeting the goals of the high-level waste transmutation program better than solid fuel reactors. In fact, they may enable doing most if not all of the transmutation planned for accelerator-driven subcritical reactors."

http://www.geocities.com/rmoir2003/2mlt_slt.htmOther, very distinguished nuclear scientist have endorced the LFTR/MSR concept.

The abstract of Edward Tellers last paper (Thorium-Fueled Underground Power Plant Based on Molten Salt Technology.), which Teller wrote with Ralph Moir, states:

"This paper addresses the problems posed by running out of oil and gas supplies and the environmental problems that are due to greenhouse gases by suggesting the use of the energy available in the resource thorium, which is much more plentiful than the conventional nuclear fuel uranium. We propose the burning of this thorium dissolved as afluoride in molten salt in the minimum viscosity mixture ofLiF and BeF[2] together with a small amount of [235]U or plutonium fluoride to initiate the process to be located at least 10 m underground. The fission products could be stored at the same underground location. With graphite replacement or new cores and with the liquid fuel transferred to the new cores periodically, the power plant could operate for up to 200 yr with no transport of fissile material to the reactor or of wastes from the reactor during this period. Advantages that include utilization of,an abundant fuel, inaccessibility of that fuel to terrorists or for diversion to weapons use, together with good economics and safety features such as an underground location will diminish public concerns. We call for the construction of a small prototype thorium-burning reactor."

http://www.geocities.com/rmoir2003/2mlt_slt.htm

My lack of authority as a scientist is not an issue in this discussion. What I am doing in my discussion is pointing to what very distinguished scientist have said. My position is that if the scientists are correct, then they are pointing to a technology that has significant advantages over current nuclear technology. The amount of money that needs to be invested in the LFTR development program which Teller and Moir recommended, would not finance the War in Iraq for a week, and would be a far more worthwhile investment.